Abstract: As an effective firefighting facility, water spray system is widely used in tunnels. Based on a 1:8 reduced scale double-layer tunnel platform (36 m long and a clear height of 0.58 m for each single-layer tunnel), this study carried out experiments in the lower deck space of the model and explored the effects of water spray system working pressure, opening time, spray section and number of opening sections on the fire control effect. Findings reveal a dual effect of water mist interaction with flames, with both enhancing flame intensity and inhibiting combustion, the latter being more pronounced with higher water spray pressures. When the water spray pressure exceeds 0.30 MPa, fire suppression becomes the dominant factor. The extinguishing time of fire source decreases with the increase of water spray sections. The earlier the water spray system is started, the more quickly and effectively the fire temperature can be controlled at alower level, while delayed activation leads to high-temperature vaporization, hindering combustion and attenuating fire progression. Importantly, the water spray sections have a significant influence on the temperature distribution in tunnel.

Key words: tunnel fire, water spray, opening time, spray pressure